The sex ratio and oogenesis of Pseudococcus citri. 165 
eloth eliminates this factor, the same activity of young larvae is 
annoying in another way. This arises from the fact that the isolated 
larvae nearly always leave the host plant in their travels, becoming 
lost and dying in the earth or on the sides of the chimney. 
Of 54 larvae isolated in March, 1920, at Washington, D. C., only 
six were raised to maturity. Three of these, isolated on March 1, 4, 
and 11 respectively, proved to be females and were kept until August 2, 
June 3, and August 3 of the same year respectively. At the time when 
the experiments were terminated, none of the three females had laid 
any eggs, although the youngest was then at least 3 months old. Four 
control females, which had been left exposed to permit fertilization by 
males from naturally infected plants in the same greenhouse, all laid 
eggs which developed and hatched. In all four cases the egg laying 
began before the expiration of 40 days. 
More recently I found that by using Bryophyllum as a host plant 
and placing the pot in water so that the base of the plant is sub- 
merged, the isolated larvae are much less apt to leave the plant, 
although even then a certain percentage is lost through drowning. 
From February 27 to March 4, 1922, a number of larvae were thus 
isolated at Bryn Mawr, Pa. Of these, eight were raised to maturity, 
five of which proved to be females. As in the previous experiments, 
all five failed to lay eggs; the test being terminated on May 29. Six 
control females, exposed as before, laid eggs before the expiration of 
46 days, and these again developed and hatched in normal manner. 
To sum up, eight virgin females were raised to maturity, and not 
a single one of them showed any indications of parthenogenesis. 
Dissection of five of these revealed varying degrees of fatty degeneration 
throughout the body. The two oldest specimen, approximately five 
months old, had very degenerate ovaries. The ova, few in number, 
were smaller than normal eggs after the growth stage and showed 
nuclear disintegration. In spite of the fatty degeneration, the bodies 
of these two specimen were shriveled, and evidently both were near 
the point of death. 
In younger virgin females, degeneration had not progressed so 
far. In case of two of the unfertilized females of the 1922 experiment, 
the chimney was removed from the plant at the expiration of the period 
mentioned above. Both commenced laying five days after this exposure, 
and normal larvae were hatched from the eggs. This indicates that 
